Strontium Sulphate

[farfalla1]

Hi all,

 

just hoping someone can help me out.... I would like to make Sr Sulphate by starting with Sr Nitrate, and potassium sulphate, but I am not sure on the amounts to use. My goal is 100gms of Sr sulphate, and I don't want to waste any of my reagents. Does anybody KNOW what the correct starting amounts/concentrations should be to get 1oo gms of final product??

 

Any help greatly appreciated.

 

Thanks

 

Tim

[mike_au]

It's been a while since I had to do this so I may stuff up, it might pay to wait until someone else posts to confirm/deny before you get started.

 

Anyway...

 

The balanced equation is Sr(NO3)2 + K2SO4 --> SrSO4 + 2KNO3

 

We go to our periodic table and find

 

K2SO4 is 2x K (Atomic weight 19), S (16) and 4x O (8) so molecular weight for K2SO4 is 2(19)+16+4(8) = 86

Sr(NO3)2 = 38+2(7+3(8)) = 100

 

and

 

SrSO4 = 38+16+4(8) = 86

 

The molecular weight is how much one mole of the substance will weigh in grams. So if you want 100g of SrSO4, you want 1.16moles of product which will need 1.16 moles of each of the reagents. So 100g of K2SO4 and 116g of SrNO3.

 

 

Whoops, those are atomic numbers not atomic weights, I'll redo this in the morning and tell you the correct answer.

Edited September 7, 2009 by mike_au

[Mumbles]

I'll pick up where mike left off. He was headed in the right direction, just made a simple error.

 

To calculate the atomic mass of a compound, you add up the molecular weights of each atom in said compound.

 

Strontium sulfate: (1 x 87.62 Sr) + (1 x 32.07 S) + (4 x 16.00 O) =183.68

 

To calculate this, I like the following site, if you don't have a periodic table handy. It has all the masses right on it, so you don't have to look up every one every time you need it.

 

http://www.ptable.com/

 

Now, I of course like cheating better. http://chembiofinder.cambridgesoft.com/che...mpleSearch.aspx You just type in the name, and you're good to go.

 

KNO3 - 101.1

Sr(NO3)2 - 211.63

K2SO4 - 174.26

 

As mike posted, the reaction is

 

K2SO4 + Sr(NO3)2 ---> SrSO4 (s) + 2 KNO3 (aq)

 

100g of SrSO4 is 100g/183.68 (grams per mol), so .544 moles. We need an equal amount of each of the two starting reagents, multiplied by the molar coefficient. In our case, we need 1 mol of Sr Nitrate, and 1 mole of Potassium sulfate, so it's not an issue. But for instance, we will be forming 1.088 moles of Potassium Nitrate. Just multiply .544 by the molar masses above, and you will get the amounts needed.

 

Sr(NO3)2 - 115.22g

K2SO4 - 94.87g

 

These amounts will in theory give you exactly 100g. You might want to bump them both up by 5-10% to account for losses and inefficiency.

[farfalla1]

Thanks Mumbles,

 

excellent answer

 

Tim

[mike_au]

Agreed, Thanks Mumbles.

 

I'm glad someone around here can remember their chemistry

[Mumbles]

Lots of practice.

[TYRONEEZEKIEL]

If I may ask, What do you do for a living mumbles? I am going into chemistry and it seems like your shoes would be a great place to be?

[Mumbles]

I'm about to graduate with my degree in Chemistry. What I do, or rather will do, is kind of up in the air right now. Grad school likely awaits.

[Yafmot]

Mumbles, do you really want to spend the next several years as a professional student? The real world is a lot more fun! Most especially if you can get some work in R&D.

 

ARDEC is always looking for chemists, CEs and engineers for the programs they're constantly cooking up. There's some question about whether an advanced degree will swing a bigger hammer when it comes to getting hired. My guess is that it would allow you to skate into a senior position (and pay scale) a lot sooner. Plus, right from the start your GS rating will be higher if you stay in academia another two years and get your Master's.

 

And there's almost a revolving door between the academic world and defense industries. Many times, I've seen a guy (or, increasingly, a girl) get their BS and go to work at, say, Raytheon, then go back to school after a couple of years, get their MS and then go back to work at another prime contractor (ATK maybe?) until they become a PhD candidate and start agonizing over losing seniority versus the pay scale they'll get when they can call themselves "doctor." It's a helluva choice, especially since, by then, there'll be a wife & kids involved, and they're not likely to sit still for Ramen noodles twice a day.

 

And all of this is weighed against how much fun you'll be having playing with the latest & greatest explosives technology in existence. If you're smack dab in the middle of a program that you have hatched & nursed along and is just about perfected, what do you do when the phone rings and it's MIT or Stanford or Cal Tech saying they have a slot open for you to get your "Piled Higher & Deeper?"

 

Decisions, decisions...

Edited November 22, 2009 by Yafmot

[Mumbles]

Yeah, I do have many decisions. Ideally I could just get a masters degree and see where things lie from there. It's not common to give straight masters degrees, without having to drop out of a PhD program. There is a place in North Carolina, a place in Denver, and a few others that offer only masters. The NC one is sort of respectable, but most anywhere that offers a terminal masters program has about as much clout and national networking capabilities as community college. No offense to anyone in community college, they have their place in the educational system, but not for what I do. I've been looking at a dual MS/MBA program a bit, which also give me a bit of a leg up as far as advancement.

 

If I am going through with a PhD, I am doing it now. I wont be coming back later in life just to be called Dr. Mumbles, or for an extra $10,000 a year. It'd be hard to return to the life I currently live after being able to afford some of the finer things

 

I don't have a great deal of contacts in the defense industry, nor know much about the big players, which make getting involved slightly difficult. It's a somewhat secretive industry, so much of the information is intentionally vague. About the closest I am currently at is applying for the DoD graduate fellowship.

 

I would love to work in the industry. I feel like it would be a good fit. I have been looking at industrial research, edging toward something perhaps at a national laboratory. Getting to combine my love of science and research, with relative freedom and things that go boom in the night would be nice.

[Arthur]

Going back to student income is hard when there are mouths to feed and a mortgage to pay.

[ActionTekJackson]

Damn I should have stayed in college.... Chemistry is so much more fun than computers....